Lysosomal dysfunction and overload of nucleosides in thymidine phosphorylase deficiency of MNGIE.

Inherited deficiency of thymidine phosphorylase (TP), encoded by TYMP, leads to a rare disease with multiple mitochondrial DNA (mtDNA) abnormalities, mitochondrial neurogastrointestinal encephalomyopathy (MNGIE). However, the impact of TP deficiency on lysosomes remains unclear, which are important for mitochondrial quality control and nucleic acid metabolism. Muscle biopsy tissue and skin fibroblasts from MNGIE patients, patients with m.3243 A > G mitochondrial encephalopathy, lactic acidosis and stroke-like episodes (MELAS) and healthy controls (HC) were collected to perform mitochondrial and lysosomal functional analyses. In addition to mtDNA abnormalities, compared to controls distinctively reduced expression of LAMP1 and increased mitochondrial content were detected in the muscle tissue of MNGIE patients. Skin fibroblasts from MNGIE patients showed decreased expression of LAMP2, lowered lysosomal acidity, reduced enzyme activity and impaired protein degradation ability. TYMP knockout or TP inhibition in cells can also induce the similar lysosomal dysfunction. Using lysosome immunoprecipitation (Lyso- IP), increased mitochondrial proteins, decreased vesicular proteins and V-ATPase enzymes, and accumulation of various nucleosides were detected in lysosomes with TP deficiency. Treatment of cells with high concentrations of dThd and dUrd also triggers lysosomal dysfunction and disruption of mitochondrial homeostasis. Therefore, the results provided evidence that TP deficiency leads to nucleoside accumulation in lysosomes and lysosomal dysfunction, revealing the widespread disruption of organelles underlying MNGIE.

Distinctive metabolic remodeling in TYMP deficiency beyond mitochondrial dysfunction.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is caused by mutations in the TYMP gene, which encodes thymidine phosphorylase (TP). As a cytosolic metabolic enzyme, TP defects affect biological processes that are thought to not be limited to the abnormal replication of mitochondrial DNA. This study aimed to elucidate the characteristic metabolic alterations and associated homeostatic regulation caused by TYMP deficiency. The pathogenicity of novel TYMP variants was evaluated in terms of clinical features, genetic analysis, and structural instability. We analyzed plasma samples from three patients with MNGIE; three patients with m.3243A > G mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS); and four healthy controls (HC) using both targeted and untargeted metabolomics techniques. Transcriptomics analysis and bioenergetic studies were performed on skin fibroblasts from participants in these three groups. A TYMP overexpression experiment was conducted to rescue the observed changes. Compared with controls, specific alterations in nucleosides, bile acids, and steroid metabolites were identified in the plasma of MNGIE patients. Comparable mitochondrial dysfunction was present in fibroblasts from patients with TYMP deficiency and in those from patients with the m.3243A > G mutation. Distinctively decreased sterol regulatory element binding protein (SREBP) regulated cholesterol metabolism and fatty acid (FA) biosynthesis as well as reduced FA degradation were revealed in fibroblasts with TYMP deficiency. The restoration of thymidine phosphorylase activity rescued the observed changes in MNGIE fibroblasts. Our findings indicated that more widespread metabolic disturbance may be caused by TYMP deficiency in addition to mitochondrial dysfunction, which expands our knowledge of the biochemical outcome of TYMP deficiency. KEY MESSAGES: Distinct metabolic profiles in patients with TYMP deficiency compared to those with m.3243A > G mutation. TYMP deficiency leads to a global disruption of nucleoside metabolism. Cholesterol and fatty acid metabolism are inhibited in individuals with MNGIE. TYMP is functionally related to SREBP-regulated pathways. Potential metabolite biomarkers that could be valuable clinical tools to improve the diagnosis of MNGIE.

Thymidine phosphorylase as a molecular target for quercetin-incorporated collagen matrix in the prevention of hand-foot syndrome induced by capecitabine in rats.

Hand-foot syndrome (HFS) is a common adverse effect of capecitabine affecting the quality of life of cancer patients. To enhance the tolerability of capecitabine, this work evaluated the incorporation of quercetin into topical collagen matrix formula to target thymidine phosphorylase enzyme, oxidative stress, and apoptosis underlying HFS. Forty Sprague Dawley rats were allocated to four equal groups. The control group received distilled water orally. HFS was induced by oral capecitabine (200 mg/kg/day) for 21 days. The untreated HFS group received no treatment. In the treated groups, topical collagen and quercetin-incorporated collagen matrix formula were administered concomitantly with the HFS induction protocol. Treatment with quercetin-incorporated collagen matrix showed a significant decrease in thymidine phosphorylase level compared with the untreated and collagen-treated groups. Treatment with quercetin-incorporated collagen matrix showed a significant decrease in malondialdehyde and caspase-3 levels, and a significant increase in the total antioxidant capacity of the skin and B cell lymphoma/leukemia 2 levels compared with the untreated group. Additionally, a significant improvement in the gross picture and histopathological score of HFS was observed. In conclusion, the quercetin-incorporated collagen matrix is a promising formula for the prevention of HFS, due to the targeted effect on thymidine phosphorylase and subsequent antioxidant and antiapoptotic effects.

Depletion of plasma thymidine results in growth retardation and mitochondrial myopathy in mice overexpressing human thymidine phosphorylase.

Plasma thymidine levels in rodents are higher than in other mammals including humans, possibly due to a different pattern and lower level of thymidine phosphorylase expression. Here, we generated a novel knock-in (KI) mouse line with high systemic expression of human thymidine phosphorylase to investigate this difference in nucleotide metabolism in rodents. The KI mice showed growth retardation around weaning and died by 4 weeks of age with a decrease in plasma thymidine level compared with the litter-control WT mice. These phenotypes were completely or partially rescued by administration of the thymidine phosphorylase inhibitor 5-chloro-6-(2-iminopyrrolidin-1-yl) methyl-2,4(1H,3H)-pyrimidinedione hydrochloride or thymidine, respectively. Interestingly, when thymidine phosphorylase inhibitor administration was discontinued in adult animals, KI mice showed deteriorated grip strength and locomotor activity, decreased bodyweight, and subsequent hind-limb paralysis. Upon histological analyses, we observed axonal degeneration in the spinal cord, muscular atrophy with morphologically abnormal mitochondria in quadriceps, retinal degeneration, and abnormality in the exocrine pancreas. Moreover, we detected mitochondrial DNA depletion in multiple tissues of KI mice. These results indicate that the KI mouse represents a new animal model for mitochondrial diseases and should be applicable for the study of differences in nucleotide metabolism between humans and mice.

Capecitabine induces hand-foot syndrome through elevated thymidine phosphorylase-mediated locoregional toxicity and GSDME-driven pyroptosis that can be relieved by tipiracil.

BACKGROUND: Hand-foot syndrome (HFS) is a serious dose-limiting cutaneous toxicity of capecitabine-containing chemotherapy, leading to a deteriorated quality of life and negative impacts on chemotherapy treatment. The symptoms of HFS have been widely reported, but the precise molecular and cellular mechanisms remain unknown. The metabolic enzyme of capecitabine, thymidine phosphorylase (TP) may be related to HFS. Here, we investigated whether TP contributes to the HFS and the molecular basis of cellular toxicity of capecitabine. METHODS: TP-/- mice were generated to assess the relevance of TP and HFS. Cellular toxicity and signalling mechanisms were assessed by in vitro and in vivo experiments. RESULTS: TP-/- significantly reduced capecitabine-induced HFS, indicating that the activity of TP plays a critical role in the development of HFS. Further investigations into the cellular mechanisms revealed that the cytotoxicity of the active metabolite of capecitabine, 5-DFUR, was attributed to the cleavage of GSDME-mediated pyroptosis. Finally, we demonstrated that capecitabine-induced HFS could be reversed by local application of the TP inhibitor tipiracil. CONCLUSION: Our findings reveal that the presence of elevated TP expression in the palm and sole aggravates local cell cytotoxicity, further explaining the molecular basis underlying 5-DFUR-induced cellular toxicity and providing a promising approach to the therapeutic management of HFS.

Recent advances in the synthetic thymidine phosphorylase inhibitors for cancer therapy.

Thymidine phosphorylase (TP) is an important enzyme for the synthesis and decomposition of pyrimidine, which can specifically catalyze the reversible phosphorolysis of thymidine to thymine and 2-deoxy-α-D-ribose-1-phosphate in the body. TP is highly expressed in many solid tumor tissues and can induce angiogenesis and anti-apoptotic effect, as well as tumor growth and metastasis. Therefore, TP inhibitors play a major role in the treatment. In recent years, a large number of synthetic TP inhibitors have been widely reported. In this article, the research progress of synthetic TP inhibitors was reviewed, including inhibitory activity, cytotoxicity, structure-activity relationship (SAR), inhibitory kinetics, mechanism of interaction and molecular docking. In our reviewed inhibitors, pyrimidine derivatives account for about a half, but it is a lack for research on other biological activities of pyrimidine derivatives and further exploration of the inhibitory mechanism of excellent inhibitors. Meanwhile, application of radiolabeled inhibitors to assess TP expression in tumors and prognosis of cancer chemotherapy in vivo is rarely reported. In addition, the study on the synergistic anticancer activity of TP inhibitors in combination with other anticancer drugs is less. Therefore, it is valuable to look forward to developing more and more potent TP inhibitors and applying them in the clinical treatment of cancer in the future.

A novel thymidine phosphorylase mutation in a family with Mitochondrial Neurogastrointestinal Encephalomyopathy (MNGIE): Molecular docking, dynamic simulation and computational investigations.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE; OMIM 603041) is a rare inherited metabolic disorder mostly caused by mutations in TYMP gene encoding thymidine phosphorylase (TP) protein that affects the mitochondrial nucleotide metabolism. TP, functionally active as a homodimer, is involved in the salvage pathway of pyrimidine nucleosides. MNGIE-like syndrome having an overlapping phenotype of MNGIE was also described and has been associated with mutations in POLG and RRM2B genes. In the present study, we report the molecular investigation of a consanguineous family including two patients with clinical features suggestive of MNGIE syndrome. Bioinformatics analyses were carried out in addition to mtDNA deletion screening and copy number quantification in the blood of the two patients. Whole exome sequencing and Sanger sequencing analyses revealed the segregation in the affected family a novel mutation c.1205T>A (p.L402Q) within the exon 9 of the TYMP gene. In addition, mtDNA analysis revealed the absence of mtDNA deletions and a decrease of the copy number in the blood of the two patients of the studied family. The p.Leu402Gln mutation was located in a conserved amino acid within the α/ß domain of the TP protein and several software supported its pathogenicity. In addition, and based on docking and molecular dynamic simulation analyses, results revealed that L402Q caused a conformational change in TP mutated structure and could therefore alter its flexibility and stability. These changes prevent also the formation of stable homodimer leading to non-functional protein with partial or complete loss of its catalytic activity.

Loss of thymidine phosphorylase activity disrupts adipocyte differentiation and induces insulin-resistant lipoatrophic diabetes.

BACKGROUND: Thymidine phosphorylase (TP), encoded by the TYMP gene, is a cytosolic enzyme essential for the nucleotide salvage pathway. TP catalyzes the phosphorylation of the deoxyribonucleosides, thymidine and 2'-deoxyuridine, to thymine and uracil. Biallelic TYMP variants are responsible for Mitochondrial NeuroGastroIntestinal Encephalomyopathy (MNGIE), an autosomal recessive disorder characterized in most patients by gastrointestinal and neurological symptoms, ultimately leading to death. Studies on the impact of TYMP variants in cellular systems with relevance to the organs affected in MNGIE are still scarce and the role of TP in adipose tissue remains unexplored. METHODS: Deep phenotyping was performed in three patients from two families carrying homozygous TYMP variants and presenting with lipoatrophic diabetes. The impact of the loss of TP expression was evaluated using a CRISPR-Cas9-mediated TP knockout (KO) strategy in human adipose stem cells (ASC), which can be differentiated into adipocytes in vitro. Protein expression profiles and cellular characteristics were investigated in this KO model. RESULTS: All patients had TYMP loss-of-function variants and first presented with generalized loss of adipose tissue and insulin-resistant diabetes. CRISPR-Cas9-mediated TP KO in ASC abolished adipocyte differentiation and decreased insulin response, consistent with the patients' phenotype. This KO also induced major oxidative stress, altered mitochondrial functions, and promoted cellular senescence. This translational study identifies a new role of TP by demonstrating its key regulatory functions in adipose tissue. CONCLUSIONS: The implication of TP variants in atypical forms of monogenic diabetes shows that genetic diagnosis of lipodystrophic syndromes should include TYMP analysis. The fact that TP is crucial for adipocyte differentiation and function through the control of mitochondrial homeostasis highlights the importance of mitochondria in adipose tissue biology.

Multifunctional role of thymidine phosphorylase in cancer.

Thymidine phosphorylase (TP) catalyzes the reversible phosphorolysis of thymidine, maintaining nucleoside homeostasis for DNA repair and replication. In many cancers TP is expressed at high levels and promotes thymidine catabolism, ultimately generating 2-deoxyribose (2dDR) that can support multiple procancer processes, including glycation of proteins, alternative metabolism, extracellular matrix remodeling, and angiogenesis. Therefore, inhibition of TP is an attractive anticancer strategy; however, an alternative approach that exploits the catalytic activity of TP to activate 5-fluorouracil (5-FU) prodrugs has been clinically successful. Here, we review the structure, function, and regulation of TP, its multiple supporting roles in cancer growth and survival. We summarize TP inhibitor and prodrug development and propose TP-targeting strategies that could potentiate the action of current therapies.

Effect of Thymidine Phosphorylase Gene Demethylation on Sensitivity to 5-Fluorouracil in Colorectal Cancer Cells.

BACKGROUND/AIM: Chemotherapy is used for recurrent and metastatic colorectal cancer, but the response rate of 5-fluorouracil (5-FU), the standard treatment for colorectal cancer, is low. We hypothesized that thymidine phosphorylase (TYMP) expression, a rate-limiting activating enzyme of 5-FU, is regulated by methylation of the gene promoter region, and demethylation of TYMP would increase sensitivity to 5-FU. MATERIALS AND METHODS: HCT116 colon cancer cells were treated with 5-aza-2'-deoxycytidine, a demethylating agent, and changes in TYMP transcription and sensitivity to 5-FU were evaluated. RESULTS: TYMP expression increased over 54-fold in HCT116 transfected with TYMP. The cytotoxicity of 5-FU increased up to 5.5-fold. In comparison, in HCT116 treated with 5-aza-2'-deoxycytidine, TYMP expression increased 5.8-fold. However, the cytotoxicity of 5-FU remained unchanged. CONCLUSION: Demethylating agent alone did not promote the cytotoxicity of 5-FU against colorectal cancer. To further increase the sensitivity to 5-FU, combination with adjuvant therapy focusing on metabolic pathways other than the TYMP pathway appear necessary.

The Janus kinase inhibitor (baricitinib) suppresses the rheumatoid arthritis active marker gliostatin/thymidine phosphorylase in human fibroblast-like synoviocytes.

Gliostatin/thymidine phosphorylase (GLS/TP) is known to have angiogenic and arthritogenic activities in the pathogenesis of rheumatoid arthritis (RA). The novel oral Janus kinase (JAK) inhibitor baricitinib has demonstrated high efficacy in RA. However, the effect of baricitinib on fibroblast-like synoviocytes (FLSs), a key component of invasive synovitis, has not been still elucidated. This study investigated whether GLS/TP production could be regulated by JAK/signal transducers and activators of transcription (STAT) signaling in FLSs derived from patients with RA. FLSs were cultured and stimulated by interferon (IFN)γ in the presence of baricitinib. Expression levels of GLS/TP were determined using reverse transcription-polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), and immunocytochemistry. Phosphorylation of STAT proteins was investigated by Western blot. In cultured FLSs, GLS/TP mRNA and protein levels were significantly induced by treatment with IFNγ and these inductions were suppressed by baricitinib treatment. Baricitinib inhibited IFNγ-induced STAT1 phosphorylation, while JAK/STAT activation played a pivotal role in IFNγ-mediated GLS/TP upregulation in RA. These results suggested that baricitinib suppressed IFNγ-induced GLS/TP expression by inhibiting JAK/STAT signaling, resulting in the attenuation of neovascularization, synovial inflammation, and cartilage destruction.

Thymidine phosphorylase induction by ionizing radiation antagonizes 5-fluorouracil resistance in human ductal pancreatic adenocarcinoma.

Chemoresistance in pancreatic ductal adenocarcinoma (PDAC) frequently contributes to failure of systemic therapy. While the radiosensitizing properties of 5-fluorouracil (FU) are well known, it is unknown whether ionizing radiation (IR) sensitizes towards FU cytotoxicity. Here, we hypothesize that upregulation of thymidine phosphorylase (TP) by IR reverses FU chemoresistance in PDAC cells. The FU resistant variant of the human PDAC cell line AsPC-1 (FU-R) was used to determine the sensitizing effects of IR. Proliferation rates of FU sensitive parental (FU-S) and FU-R cells were determined by WST-1 assays after low (0.05 Gy) and intermediate dose (2.0 Gy) IR followed by FU treatment. TP protein expression in PDAC cells before and after IR was assessed by Western blot. To analyze the specificity of the FU sensitizing effect, TP was ablated by siRNA. FU-R cells showed a 2.7-fold increase of the half maximal inhibitory concentration, compared to FU-S parental cells. Further, FU-R cells showed a concomitant IR resistance towards both doses applied. When challenging both cell lines with FU after IR, FU-R cells had lower proliferation rates than FU-S cells, suggesting a reversal of chemoresistance by IR. This FU sensitizing effect was abolished when TP was blocked by anti-TP siRNA before IR. An increase of TP protein expression was seen after both IR doses. Our results suggest a TP dependent reversal of FU-chemoresistance in PDAC cells that is triggered by IR. Thus, induction of TP expression by low dose IR may be a therapeutic approach to potentially overcome FU chemoresistance in PDAC.

Polycyclic nitrogen heterocycles as potential thymidine phosphorylase inhibitors: synthesis, biological evaluation, and molecular docking study.

New polycyclic heterocycles were synthesised and evaluated as potential inhibitors of thymidine phosphorylase (TP). Inspired by the pharmacophoric pyrimidinedione core of the natural substrate, four series have been designed in order to interact with large empty pockets of the active site: pyrimidoquinoline-2,4-diones (series A), pyrimidinedione linked to a pyrroloquinoline-1,3-diones (series B and C), the polycyclic heterocycle has been replaced by a pyrimidopyridopyrrolidinetetraone (series D). In each series, the tricyclic nitrogen heterocyclic moiety has been synthesised by a one-pot multicomponent reaction. Compared to 7-DX used as control, 2d, 2l, 2p (series A), 28a (series D), and the open intermediate 30 showed modest to good activities. A kinetic study confirmed that the most active compounds 2d, 2p are competitive inhibitors. Molecular docking analysis confirmed the interaction of these new compounds at the active binding site of TP and highlighted a plausible specific interaction in a pocket that had not yet been explored.

Vesicular IFN-γ as a cooperative attacker to enhance anti-cancer effect of 5-fluorouracil via thymidine phosphorylase upregulation and tumor microenvironment normalization.

On the basis of immuno-modulating effect and upregulating the activity of thymidine phosphorylase (TP), interferon-γ (IFN-γ) as a cooperative attacker was explored to enhance the anticancer activity of 5-fluorouracil (5-FU). We designed and prepared a self-assembled nano-vesicular system IFN-γ-EDP formulated by amphiphilic poly((polyethylene glycol)(dodecylphosphoethanolamine)phosphazene) (EDP) to entrap IFN-γ in the hydrophilic cavity. The IFN-γ-EDP vesicles allowed IFN-γ to accumulate at the tumor site and be taken up by tumor cells, resulting in significantly upregulated expression level of TP, distinct inhibition of cell growth, more cellular apoptosis and more serious cell cycle arrest when administrated combined with 5-FU. Moreover, IFN-γ-EDP could normalize the tumor microenvironment by enhancing the CD4+ and CD8+ T cell populations, promoting the IL-12 secretion and suppressing the IL-10 secretion in tumor. As a consequence, the combination therapy of IFN-γ-EDP with 5-FU achieved remarkably enhanced tumor inhibition rate of 56.9% against CT26 colorectal cancer.

The Association of Thymidine Phosphorylase with Gastric Cancer Prognosis.

BACKGROUND: Thymidine phosphorylase(TP)plays an important role in angiogenesis and solid tumor invasion. This study aimed to investigate TP expression in gastric cancer(GC), its correlation with clinicopathological features, and its prognostic significance. METHODS: Clinical data and tumor specimens were retrospectively collected from patients with GC in Ikeda Municipal Hospital between January 2005 and December 2006. Tumor specimens were immunohistochemically analyzed for TP expression graded as 0, 1+, 2+, or 3+ and divided into low(0/1+)and high(2+/3+)TP expression groups. To determine its potential prognostic value, any correlation between TP expression and the clinicopathological features of the patients was statistically assessed. RESULTS: Among 111 patients with GC, 33 had high TP expression(29.7%)and 78 had low TP expression(70.3%). There were significant differences in tumor size, tumor depth, venous invasion, lymphatic invasion, and clinical stage between the two groups. Analysis of the Kaplan-Meier survival curves revealed that the high TP group had significantly shorter overall survival(OS; p<0.01)and progression-free survival(PFS; p<0.01)than the low TP group. Moreover, the high TP group had significantly shorter OS(p=0.040)and a trend toward a shorter PFS(p=0.064) than the low TP group in patients with stage Ⅱ, Ⅲ, and Ⅳ cancer. Multivariate analysis revealed that high TP expression was significantly associated with tumor size, tumor type, and lymphatic invasion in patients with GC. CONCLUSIONS: Our results suggest that high TP expression might predict poor prognosis in GC.

A novel near-infrared theranostic probe for accurate cancer chemotherapy in vivo by a dual activation strategy.

A novel theranostic probe called CX-B-DF is constructed for precise chemotherapy guided by near-infrared (NIR) fluorescence imaging. Moreover, the theranostic probe shows high cytotoxicity to cancer cells under dual activation (H2O2 and TP), which causes the accuracy of drug release to be improved and the toxic side effects to be reduced.

Capecitabine Can Induce T Cell Apoptosis: A Potential Immunosuppressive Agent With Anti-Cancer Effect.

Capecitabine (CAP) is now widely used in the comprehensive treatment of digestive system tumors. Some clinical observations have shown that CAP may have immunosuppressive effects, but there is still a lack of clear experimental verification. In this study, different doses of CAP were administered to normal mice by gavage. Our results confirmed that CAP did not cause myelosuppression in bone marrow tissue; CAP selectively reduced the proportion of T cells and the concentration of related pro-inflammatory cytokines, while it increased the concentration of anti-inflammatory cytokines. Thymidylate phosphorylase (TP) is the key enzyme for the transformation of CAP in vivo; this study confirmed that T cells express TP, but the bone marrow tissue lacks TP expression, which explains the selectivity in pharmacodynamic effects of CAP. In addition, it was confirmed that CAP can induce T cell apoptosis in vivo and in vitro. In vitro experiments showed that CAP-induced T cell apoptosis was related to TP expression, endoplasmic reticulum stress (ERS) induction, reactive oxygen species (ROS) production, and mitochondria-mediated apoptosis activation. Therefore, this study confirmed that the differential expression of TP in cells and tissues explains why CAP avoids the toxic effects of myelosuppression while inducing T cell apoptosis to exert the immunosuppressive effect. Therefore, CAP may become an immunosuppressive agent with a simultaneous anti-cancer effect, which is worthy of further studies.

Design, synthesis, modelling studies and biological evaluation of 1,3,4-oxadiazole derivatives as potent anticancer agents targeting thymidine phosphorylase enzyme.

A series of novel 1,3,4-oxadiazole derivatives with substituted phenyl ring were designed and synthesized with an objective of discovering newer anti-cancer agents targeting thymidine phosphorylase enzyme (TP). The 1,3,4-oxadiazole derivatives were synthesized by simple and convenient methods in the lab. Chemical structure of the all the synthesized compounds were characterized by IR, 1H NMR and mass spectral methods and evaluated for cytotoxicity by MTT method against two breast cancer cell lines (MCF-7 and MDA-MB-231). Further, results of TP assay identified that 1,3,4-oxadiazole molecules displayed anti-cancer activity partially by inhibition of phosphorylation of thymidine. The TP assay identified SB8 and SB9 as potential inhibitors with anti-cancer activity against both the cell lines. The molecular docking studies recognized the orientation and binding interaction of molecule at the active site amino acid residues of TP (PDB: 1UOU). Acute toxicity studies of compound SB8 at the dose of 5000 mg/kg has identified no signs of clinical toxicity was observed. The SARs study of synthesized derivatives revealed that the substitution of phenyl ring with electron withdrawing group at ortho position showed significant TP inhibitory activity compared to para substitution. The experimental data suggests that 1,3,4-oxadiazole with substituted phenyl can be taken as a lead for the design of efficient TP inhibitors and active compounds which can be taken up for further studies.

Novel Mutations of the TYMP Gene in Mitochondrial Neurogastrointestinal Encephalomyopathy: Case Series and Literature Review.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a multi-system disorder caused by several homozygous or compound heterozygous mutations, mostly in the nuclear gene of TYMP. Our current knowledge on the underlying pathology of the disease is derived through the study of about 200 cases of different ethnicities. Clinical presentations include severe cachexia, weakness, ptosis, diplopia, abdominal cramps or digestive tract disorders, hearing impairment, and paresthesia.Herein, we aim to present five novel mutations of the nuclear gene of TYMP in six Iranian patients diagnosed with MNGIE. In our population, age at the time of diagnosis was 18 to 49 years, while the onset of the symptoms varied from 13 to 20 years. We detected two pathogenic non-frameshift nonsense premature stop codon mutations (c.1013C > A, and c.130C > T), one variant of uncertain significance (VUS) non-frameshift missense mutation (c.345G > T), one likely pathogenic frameshift insertion (c.801_802insCGCG), and one likely benign homozygous non-frameshift deletion (c.1176_1187del) from two siblings. Our findings also confirm the autosomal recessive inheritance pattern of MNGIE in the Iranian population. The lack of knowledge in the area of nuclear gene-modifier genes shadows the genotype-phenotype relationships of MNGIE.

Evidence of enteric angiopathy and neuromuscular hypoxia in patients with mitochondrial neurogastrointestinal encephalomyopathy.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a rare autosomal recessive disease caused by thymidine phosphorylase (TP) enzyme defect. As gastrointestinal changes do not revert in patients undergone TP replacement therapy, one can postulate that other unexplored mechanisms contribute to MNGIE pathophysiology. Hence, we focused on the local TP angiogenic potential that has never been considered in MNGIE. In this study, we investigated the enteric submucosal microvasculature and the effect of hypoxia on fibrosis and enteric neurons density in jejunal full-thickness biopsies collected from patients with MNGIE. Orcein staining was used to count blood vessels based on their size. Fibrosis was assessed using the Sirius Red and Fast Green method. Hypoxia and neoangiogenesis were determined via hypoxia-inducible-factor-1α (HIF-1α) and vascular endothelial cell growth factor (VEGF) protein expression, respectively. Neuron-specific enolase was used to label enteric neurons. Compared with controls, patients with MNGIE showed a decreased area of vascular tissue, but a twofold increase of submucosal vessels/mm2 with increased small size and decreased medium and large size vessels. VEGF positive vessels, fibrosis index, and HIF-1α protein expression were increased, whereas there was a diminished thickness of the longitudinal muscle layer with an increased interganglionic distance and reduced number of myenteric neurons. We demonstrated the occurrence of an angiopathy in the GI tract of patients with MNGIE. Neoangiogenetic changes, as detected by the abundance of small size vessels in the jejunal submucosa, along with hypoxia provide a morphological basis to explain neuromuscular alterations, vasculature breakdown, and ischemic abnormalities in MNGIE.NEW & NOTEWORTHY Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is characterized by a genetically driven defect of thymidine phosphorylase, a multitask enzyme playing a role also in angiogenesis. Indeed, major gastrointestinal bleedings are life-threatening complications of MNGIE. Thus, we focused on jejunal submucosal vasculature and showed intestinal microangiopathy as a novel feature occurring in this disease. Notably, vascular changes were associated with neuromuscular abnormalities, which may explain gut dysfunction and help to develop future therapeutic approaches in MNGIE.